An important criterion for optimum core sand mixtures is, apart from a good surface of the casting and good core stability up to the time of casting, good disintegration of the blank following casting. This significantly influences the amount of cleaning to be carried out on the rough casting. Therefore what is sought consists of core molding material mixtures which, as cores after casting, have a maximum amount of burnt molding material (detachment from the casting inner wall) and ensure a rapid residual material disintegration from the casting during jolting.
Numerous modern, efficient core shooting machines are commercially available for the production of sand cores according to various core production processes. Known core production processes are the shell molding process (Croning process), the hot box process, the cold box process, the carbon dioxide solidification process and the SO.sub.2 process.
It is necessary in each of these processes, when introducing the sand mixture for the core, vents are available from which the air which must give way for core formation can escape. In certain other processes, even following core production, this is scavenged e.g. with carbon dioxide, a catalyst mist or CO.sub.2, e.g. in order to bring about its complete hardening.
The corresponding bores for venting purposes or for introducing the scavenging medium are now normally occupied by nozzles, which have cross-barred slits or small holes. The corresponding recesses for the nozzles are generally drilled, which involves additional working operations. As a core box can have 100 or more nozzles, so that the core can be correctly vented throughout or sand can flow into unfavourable positions, or the core box is filled in an adequate and uniformly compressed manner, said subsequent operation is very complicated and costly.